1. Field of the Invention
The present invention relates to a cleaning method of cleaning substrates of various kinds, such as semiconductor wafers and LCD substrates, by a processing liquid and also relates to a cleaning apparatus for carrying out the above cleaning method.
2. Description of the Related Art
In the manufacturing process of the semiconductor devices, the semiconductor wafers as the substrates are processed by a processing liquid, such as designated chemical liquids and pure water, in order to remove contaminations (e.g. particles, organic contaminants and metallic impurities), organic substances and oxidization films, out of the wafers.
When carrying out this cleaning process by using the pure water, there is used CO2 injection water of which resistivity is lowered by dissolving carbon dioxide (CO2) gas into the pure water, in order to avoid the generation of static electricity during the cleaning process, which might cause discharge breakdown on the wafers.
The CO2 injection water is produced, for example, by allowing carbon dioxide through filters, such as counter-permeable membrane, to dissolve carbon dioxide into the pure water.
During the production of the CO2 injection water, the resistivity of the finished CO2 injection water is always measured and further the so-measured value is fed back for the present dissolution control of carbon dioxide to attain a designated resistivity of the water.
However, when the cleaning apparatus is equipped with such a production unit of the CO2 injection water, there come into existence problems that the installation cost is elevated and the apparatus itself is large-sized, due to the establishment of additions, for example, filters, a resistivity meter, a feedback unit, etc. From this point of view, it is deemed that a more simple and convenient method of allowing the resistivity of pure water to be reduced is desirable to restrict the occurrence of static electricity for prevention the discharge breakdown on the wafers.
Meanwhile, in the cleaning process using various chemical liquids preceding the cleaning step using the pure water, there is a case of using a chemical liquid of organic-amine type. In this particular case, alkaline substances are produced after the cleaning process of the pure water following the cleaning process using the chemical liquid of organic-amine type, due to the reaction of the chemical liquid with the pure water. Unfortunately, the alkaline substances erode aluminum wiring on the wafers. In this view, it is also desired to prevent the generation of alkaline substances derived from the reaction of the chemical liquid with the pure water.
Hereat, it is noted that the manufacturing process of semiconductor wafers comprises the following steps of: forming oxidation layers (SiO2), nitride layers (SiN), metal layers (Cu) or the like on the wafers; applying resists on the wafers; exposing a designated pattern to each resist on the wafers and next developing the resist by developer; dry-etching oxidation layers (SiO2), nitride layers (SiN), metal layers (Cu) or the like; cleaning the wafers by a chemical liquid, such as organic solvent, organic acid, inorganic acid, etc. (for removal of residuals, e.g. polymers); and finally rinsing the used chemical liquid from the wafers, in that order.
As to the method of cleaning the wafers by the chemical liquid, there is a known method of supplying the chemical liquid to the rotating wafers. Here, it should be noted that there exist linear grooves and holes on the wafer surface, which are resulting from the etching step. Since there is a difference between flat potions on the wafer surface and the grooves/holes thereon in respect of the flowing condition of the chemical liquid, it is impossible to remove polymers sticking to the wafer perfectly in the conventional method. For this reason, it requires a long period for the chemical-processing process, causing the reduction of throughput.
Accordingly, the first object of the present invention is to provide a method for dissolving carbon dioxide in the pure water for cleaning substrates with ease and convenience.
The second object of the present invention is to provide a method for restricting the generation of alkaline substances resulting from the reaction of a chemical liquid of organic-amine type with the pure water in the cleaning process for the substrates.
The third object of the present invention is to provide a method of cleaning a surface of the substrate having grooves and holes formed thereon, effectively.
In order to accomplish the above objectives, the present invention provides a method of cleaning a substrate in a processing chamber, which includes the steps of: (a) introducing carbon dioxide gas into the processing chamber, thereby making an atmosphere of carbon dioxide concentration being greater than that of air in the processing chamber; and (b) spraying the substrate with pure water while rotating the substrate in the processing chamber having the atmosphere of carbon dioxide.
The present invention also provides a substrate cleaning apparatus, which includes: a substrate holder that holds a substrate; a motor that rotates the substrate holder; an enclosure defining a processing chamber therein, the processing chamber being capable of accommodating the substrate holder; a carbon dioxide gas supply system that supplies carbon dioxide gas into the processing chamber; and a pure water supply nozzle that sprays the substrate accommodated in the processing chamber with pure water.
In addition, the present invention also provides a method of cleaning a substrate, which includes the steps of: (a) supplying the substrate with a chemical liquid for dissolving unnecessary substances sticking to the substrate while rotating the substrate at a first rotating speed; (b) supplying the substrate with the chemical liquid while rotating the substrate at a second rotating speed greater than the first rotating speed; and (c) stopping supplying the chemical liquid and rotating the substrate at a third rotating speed greater than the second rotating speed.
Furthermore, the present invention also provides a substrate cleaning apparatus, which includes: a substrate holder that holds a substrate; a motor that rotates the substrate holder; a nozzle that sprays the substrate with a chemical liquid for dissolving unnecessary substances sticking to the substrate; and a controller that controls a rotation of the motor and an ejection of the chemical liquid from the nozzle according to a routine including the steps of: (a) supplying the substrate with the chemical liquid while rotating the substrate at a first rotating speed; (b) supplying the substrate with the chemical liquid while rotating the substrate at a second rotating speed greater than the first rotating speed; and (c) stopping supplying the chemical liquid and rotating the substrate at a third rotating speed greater than the second rotating speed.